GCN Circular 31132
Subject
Fermi-LAT Gamma-ray Observations of IceCube-211125A
Date
2021-11-26T18:17:19Z (3 years ago)
From
Simone Garrappa at DESY <simone.garrappa@desy.de>
S. Garrappa (DESY-Zeuthen), S. Buson (Univ. of Wuerzburg) and R. de
Menezes (Univ. of Wuerzburg, Univ. of Sao Paulo) on behalf of the
Fermi-LAT collaboration:
We report an analysis of observations of the vicinity of the high-energy
IC211125A neutrino event (GCN 31126) with all-sky survey data from the
Large Area Telescope (LAT), on board the Fermi Gamma-ray Space
Telescope. The IceCube event was detected on 2021-11-25 at 06:22:21.56
UT (T0) with J2000 position RA = 43.59 (+ 3.13, - 2.71) deg, Decl. =
22.59 (+ 1.54, - 2.53) deg (90% PSF containment). Two cataloged
gamma-ray (>100 MeV) sources are located within the 90% IC211125A
localization region (4FGL-DR2, The Fermi-LAT collaboration 2020, ApJS,
247, 33). These are 4FGL J0248.0+2232 at 1.46 deg distance, which is
associated with the blazar of uncertain type 1RXS J024800.1+223136, and
4FGL J0258.1+2030 at 2.26 deg distance, which is associated with the BL
Lac object MG3 J025805+2029. Based on a preliminary analysis of the LAT
data over the 1-month timescale before T0, these objects are not
significantly detected at gamma-rays.
We searched for the existence of intermediate (months to years)
timescale emission from a new gamma-ray transient source. Preliminary
analysis indicates no significant (> 5 sigma) new excess emission (> 100
MeV) at the IC211125A best-fit position. Assuming a power-law spectrum
(photon index = 2.0 fixed) for a point source at the IC211125A best-fit
position, the >100 MeV flux upper limit (95% confidence) is < 2.0e-10 ph
cm^-2 s^-1 for ~13-years (2008-08-04 to 2021-11-25 UTC), and < 1.1e-8��
ph cm^-2 s^-1 for a 1-month integration time before T0.
Due to the current Fermi-LAT observing profile
(https://fermi.gsfc.nasa.gov/ssc/observations/types/post_anomaly/) the
region of IC211125A is not observable by the LAT since November 12,
2021. Regular monitoring of this region will be resumed at the beginning
of December
(https://fermi.gsfc.nasa.gov/ssc/observations/timeline/posting/). For
these observations the Fermi-LAT contact persons are S. Garrappa
(simone.garrappa at desy.de) and S. Buson (sara.buson at uni-wuerzburg.de).
The Fermi-LAT is a pair conversion telescope designed to cover the
energy band from 20 MeV to greater than 300 GeV. It is the product of an
international collaboration between NASA and DOE in the U.S. and many
scientific institutions across France, Italy, Japan and Sweden.